Alzheimer's disease (AD) is the major cause of dementia in the elderly in Western countries, and is characterized by the progressive accumulation of intracellular neurofibrillary tangles, extracellular parenchymal senile plaques, and cerebrovascular deposits (Sissodia et al. FASEB. J. 9:366-370 (1995)). The principal component of senile plaques and cerebrovascular deposits is the β-amyloid peptide, the aggregated form of which consists of the 39-43 amino acid residue Aβ peptides that are proteolytically derived from the amyloid precursor protein (APP) (Naidu et al. J. Biol. Chem. 270:1369-1374 (1995)). Vascular pathology is the norm in advanced cases of AD, with cerebral amyloid angiopathy (CAA) being one of the most common abnormalities detected at autopsy (Ellis et al. Neurology 46:1592-1596 (1996)). Certain vascular lesions, such as microvascular degeneration affecting the cerebral endothelium and periventricular white matter lesions, are evident in most AD cases (Ellis et al. Neurology 46:1592-1596 (1996); Kalaria, Ann. N.Y. Acad. Sci. 893:113-125 (1999)). Furthermore, morphological alterations have been observed in AD brain microvessels and capillaries; in particular, terminal arterioles frequently have focal constriction and smooth muscle cells with an irregular shape and arrangement (Hashimura et al. Jpn. J. Psychiatry Neurol. 45:661-665 (1991)). Capillaries in AD brain typically show an abnormal abluminal surface with irregular constriction and dilatation along their paths (Kimura et al. Jpn. J. Psychiatry Neurol. 45:671-676 (1991)). Functional imaging techniques including positron emission tomography (PET) and single photon emission computerized tomography (SPECT) have revealed the existence of hypoperfusion in individuals prior to the time that they meet clinical criteria for AD suggesting that vascular abnormalities occur early during the disease process (Nagata et al. Neurobiology of Aging 21:301-307 (2000); Johnson et al. Neurobiology of Aging 21:289-292 (2000)). In other disorders involving cerebrovascular damage (such as traumatic brain injury, stroke and brain arteriovenous malformation), angiogenesis is a prominent response (Mendis et al. Neurochem. Res. 23:1117-23 (1998); Slevin et al. Stroke 31:1863-70 (2000); Hashimoto et al. Circ. Res. 89:111-3 (2001)). Given the plethora of reports on cerebrovascular damage in AD brain, the induction of an angiogenic reparative response would be expected, although there has been very little work in this area.
Several assays have been developed to study the specific steps involved in the angiogenic process (adhesion, migration, growth, invasion and differentiation). Knowledge of the effects of Aβ on angiogenesis would be of value in understanding its role in the micro-cerebrovascular abnormalities observed in AD.